The present invention relates to an encoding system for subband coding of a wideband digital signal, for example, a digital signal having a specific sampling frequency F.sub.S. The encoding system comprises: (a) a splitter unit which divides the bandwidth of the wideband digital signal into M successive subbands which augment with frequency, and generates, in response to the wideband digital signal, P subband signals with sampling frequency reduction, each of the subband signals being associated with one of the subbands; (b) a quantizer unit for quantizing block-by-block the respective subband signals, a subband signal SB.sub.m of the subband signals being composed of successive signal blocks, each signal block comprising q samples, the q samples in a quantized signal block of subband signal SB.sub.m each being represented by n.sub.m bits; (c) a bit need determining unit for determining bit needs for corresponding (i.e., time-equivalent) signal blocks of the subband signals, a signal block of subband signal SB.sub.m having a bit need b.sub.m which is related to the number of bits by which the q samples in that signal block should be represented; and (d) a bit allocation unit for allocating bits from an available quantity of bits B to the samples in the time-equivalent signal blocks of the subband signals in response to the bit needs determined by the bit need determining unit, such allocation establishing the value of n.sub.m ; where 1.ltoreq.m.ltoreq.P. The encoding system may further comprise a formatting circuit for assembling the quantized samples of the time-equivalent signal blocks to form an output signal having successive frames and including scale factor information in each frame, which scale factor information comprises x-bit words, an x-bit word representing a scale factor associated with the samples in a signal block. The present invention also relates to a transmitter comprising such an encoding system. An encoding system of the aforesaid type is known from U.S. Pat. No. 4,896,362.
Subband encoding of a single signal, such as a mono audio signal or a left or right signal portion of a stereo signal, may be desired. In that case P, the number of subband signals equals M, the number of subbands. In each subband, the splitter unit then generates one subband signal. However, such encoding may also involve a stereo signal. In that case, it holds that P equals 2M. The splitter unit then generates two subband signals in each subband, i.e., a left and a right subband signal.